Field of the Invention
The present invention relates to a terminal-cover assembly for a battery, particularly to a terminal-cover assembly for a secondary battery, whose electric-conduction terminals have high-hardness fastening elements.
Description of the Related Art
In order to output higher voltage, several secondary batteries are cascaded at the electric-conduction terminals thereof by electric-conduction plates to form a battery assembly.
Refer to FIG. 1 for a conventional secondary battery assembly. In FIG. 1, a fastening element 72 passes through an electric-conduction plate 74 and fastens the electric-conduction plate 74 to an electric-conduction terminal 70. The same process is repeated to electrically connect the electric-conduction terminals 70 of several batteries in series sequentially to form a battery assembly. The fastening elements 72 and the electric-conduction plates 74 will be assembled to and disassembled from the electric-conduction terminals 70 repeatedly during usage. The electric-conduction terminals 70 are normally made of high-conductivity metals, such as copper or aluminum, and the fastening elements 72 are normally made of stainless steel. The hardness of copper or aluminum is lower than the hardness of stainless steel. Thus, the repeated assembly and disassembly of the fastening elements 72 will wear and damage the female threads inside the electric-conduction terminals 70.
The fastening elements 72 and the electric-conduction terminals 70 are made of different materials and thus have different thermal expansion coefficients. The temperature of batteries rises during operation. The rising temperature makes the fastening elements 72 and the electric-conduction terminals 70 deform to different extents, and thus loosens the contact of the fastening elements 72, the electric-conduction plates 74 and the electric-conduction terminals 70. The loosened contact may further cause the impedance to rise and the batteries to overheat.
Accordingly, the present invention proposes a terminal-cover assembly for a secondary battery to overcome the abovementioned problems.